Gaseous media, for example, air are used as process agents in production processes which vary greatly. Typically, the gaseous medium must have certain properties for the respective production process, such as having a given degree of purity or a minimum moisture content. Known plate-type heat exchangers are employed to dry a gaseous medium, for instance, pressurized air so that the resulting gaseous medium to be used as a process agent will have only a predetermined degree of moisture. To accomplish that, the gaseous medium is supplied through an inlet connection into a plate-type heat exchanger. Having been thus fed, the moist inlet gas stream flows through a gas-gas heat exchanger. The gas-gas heat exchanger is formed in the plate-type heat exchanger in a portion of the stack of plates which are interconnected to define flow spaces between the plates. In the known plate-type heat exchanger the moist inlet gas stream flows away from the inlet connection and a dried outlet gas stream flows towards an outlet connection, possibly to be returned into the production process, the two streams flowing through separate flow spaces in the stack of plates. The moist inlet gas stream and the dried outlet gas stream flow in countercurrent, whereby the moist inlet gas stream, on the one hand, is precooled. On the other hand, the dried outlet gas stream is heated by thermal transfer from the moist inlet gas stream to the previously dried outlet gas stream.
The moist inlet gas stream passes from the gas-gas heat exchanger into a gas-coolant heat exchanger in the stack of plates. The gas-coolant heat exchanger likewise comprises a plurality of flow spaces between the plates of the stack. In the gas-coolant heat exchanger, the precooled inlet gas stream and a cooling agent flow in countercurrent, whereby the moist inlet gas stream is cooled down, leading to subsequent condensation of the moisture particles in the inlet gas stream so that the inlet gas stream becomes dry. The resulting dried outlet gas stream flows through an overflow member from the outlet of the gas-coolant heat exchanger to the gas-gas heat exchanger where it is heated again by absorption of heat from the incoming inlet gas stream. The outlet gas stream thus heated flows through the outlet connection of the plate-type heat exchanger towards further use.
Due to pressure conditions prevailing in the gas-gas heat exchanger and in the gas-coolant heat exchanger the overflow member, too, must fulfill strict requirements regarding resistance to pressure.
It is, therefore, an object of the invention to provide a plate-type heat exchanger for drying a gaseous medium which will allow and withstand high pressurization under operating conditions, thereby guaranteeing that safety standards are complied with.
The object is met, in accordance with the invention, by a plate-type heat exchanger as recited in independent claim 1.